Taxonomic Notes: Duellman et al. (Zootaxa 2016) treated two major clades as genera; AmphibiaWeb treats these two clades as subgenera(Hyla in the Old World; Dryophytes in the New World and East Asia), thus stabilizing traditional taxonomy.

This moderately large North American frog is a wide-ranging species. The males are usually slightly smaller than the females. A pointed snout and flat head possessing two transverse rows of vomerine teeth are also observed. The toe pads on Hyla cinerea are large. The hind feet display extensive webbing and have two metatarsal tubercles between the toes. Some populations have individuals that lack lateral stripes, but normally H. cinerea exhibits a lateral white or yellow stripe from the jaw to the thigh on either side of the body. White or yellow spots are often scattered on the back. The external, subgular vocal sac is mostly white or yellow in males when not inflated. During breeding season, the sides of the sac may turn green.

The size of tadpoles ranges from 4.5-5.5 mm from hatching and may grow to 60 mm before metamorphosis in a 28-44 day span. Until tadpoles reach stage 25 or 26, they display continuous ontogenetic color changes. After this period, the body turns green and the venter turns yellow. The tail may have distinct yellow orbitonasal stripes, and dark mottling or reticulations. Large tadpoles sometimes retain the yellow interorbital stripe. A long tail, bulging lateral eyes, dextral anus and sinistral spiracle are other morphological features of the tadpole from this species.

Adults of this species normally turn to an ashen gray color when in preservative. The normally unobserved dorsolateral stripes in living species also appear over the subcutaneous insertions of lymph-sac septa. After months in preservation, H. cinerea displays a mostly dark green or brownish color
(Conant and Collins 1998).

The habitats most likely to house H. cinerea are swamps, sloughs and weedy margins of lakes and ponds. The lower Atlantic and Gulf Coastal Plains and the lower Mississippi River drainage are ideal locations of the species' environment (Connant and Collins 1998) . The range in the Mississippi River extends from Louisiana and Mississippi to the floodplains of southern and eastern Arkansas, western Tennessee and Kentucky. Southeastern Missouri and southern Illinois are also in this range. The Atlantic/Gulf Coastal range extends from the Chesapeake Bay and Virginia to the Carolinas, Georgia, and Florida. Most of Alabama, Mississippi and all of Louisiana complete the range.

Introduced populations of this frog have been documented in Puerto Rico
(Hedges 1996; 1999; Powell et al. 1996; Rivero 1998; Schwartz and Thomas 1975; Schwartz and Henderson 1985; 1991)
,
central Missouri
(Johnson 2000) , a coastal island in Florida
(Smith et al. 1993), and in Brownsville, Texas
(Conant 1977; Smith and Kohler 1977).
A population in east central Kansas that was once introduced to a fish farm has most likely been extirpated (Collins 1993).

Life History, Abundance, Activity, and Special Behaviors

A series of nasal barks described as sounding like "frank frank frank" or "quonk quonk quonk" have been observed as breeding vocalizations.

A complete reference of breeding vocalizations may be found in the Catalogue of American Amphibians and Reptiles.

Langowski et al. (2018) revealed new insights on the biomechanics of how frogs attach to (and detach from) surfaces by examining the toe pads of the American Green treefrog (Hyla cinerea) with new technologies. Using a combination of histology, immunohistochemistry, and synchrotron micro-computer-tomography (l-CT), the researchers obtained an extremely detailed 3-D characterization of tree frog toe pads. All toe pads examined shared a general layout with a ventral collagen layer, collateral ligaments, a septum compartmentalizing the subcutaneous volume into a distal lymph space and a proximal gland space, and muscular structures. Perhaps most interestingly, the collagen layer can withstand a shear load of up to 6.5 N! Furthermore, the researchers hypothesize that the septum facilitates proximal peeling of the pad and detachment from surfaces. With this new knowledge, researchers can better explain the mechanics and physics behind frog climbing and expect that frog toe pads will help design biomimetic adhesives (Written by Molly Womack).

This species was featured as News of the Week on 5 August 2019:

The permeable skin of amphibians makes them particularly vulnerable to chemicals in their environments, including salt, which can slow down development or even cause death at high enough levels. However, a few amphibians lay their eggs in brackish water, begging the question of how these critters survive salt exposure. In a recent study, Albecker and McCoy (2019) found that coastal populations of Hyla cinerea, the American Green Treefrog, survive better and grow faster in salty environments than their inland counterparts. The authors suggest that Green Treefrogs have evolved to tolerate high salt levels in part by shortening their larval period and reducing the length of time the tadpoles are exposed to high salt levels. Future studies may reveal how these coastal frogs process higher levels of salt with specialized physiology (Written by Rebecca Tarvin).

Collins, J. T. (1993). Amphibians and Reptiles in Kansas: Third Edition, revised. University of Kansas Museum of Natural History, Lawrence.

Conant, R. (1977). ''The Florida Water Snake (Reptilia, Serpentes, Colubridae) established at Brownsville, Texas, with comments on other herpetological introductions in the area.'' Journal of Herpetology, 11(2), 217-220.

Conant, R. and Collins, J.T. (1998). A Field Guide to Reptiles and Amphibians of Eastern and Central North America. 3rd Edition. Houghton Mifflin Company, Boston, Massachusetts.

Hedges, S. B. (1996). ''The origin of West Indian amphibians and reptiles.'' Contributions to West Indian Herpetology: A Tribute to Albert Schwartz. R., Powell and R. W., Henderson, eds., Ithaca, New York, 95-128.